Refrigeration control apparatus



REFRIGERATION CONTROL APPARATUS Filed Jan. 22, 1969 Key 5 e UnitedStates Patent C) 3,498,075 REFRIGERATION CONTROL APPARATUS William A.Zumbiel, 85 Dudley Road, South Fort Mitchell, Ky. 41017Continuation-impart of application Ser. No. 680,379,

Nov. 3, 1967. This application Jan. 22, 1969, Ser.

Int. Cl. F25b 25/00 U.S. Cl. 62--209 8 Claims ABSTRACT OF THE DISCLOSUREA refrigeration system including a pressure actuated switch forcontrolling the refrigeration compressor. The switch is actuated bychanges of pressure in the' refrigerant of the system but is isolatedfrom the refrigerant by a fluid filled capillary tube having pressureactuators at its opposite ends, one of which senses changes ofrefrigerant pressure and the other of which senses changes in conditionof the rst pressure actuator and effects changes in the condition of thecontr-ol switch.

This application is a continuation-in-part application of co-pendingapplication Ser. No. 680,379, tiled Nov. 3, 1967, and now abandoned.

Background of the invention The majority of all commercial refrigerationor air conditioning systems operate upon the principal of compressing arefrigerant in a compressor, passing the compressed refrigerant througha condenser to remove heat from the compressed refrigerant and thenpassing the cooled and compressed refrigerant through an expansion valveand evaporator back to the compressor. In passing through theevaporator, the refrigerant picks up heat from the surroundingatmosphere so as to cool that atmosphere. Refrigerant flow is generallycontrolled by controlling operation of the compressor; in other words,by turning the compressor on and -otf depending upon the temperature ofthe area to be cooled.

To control actuation of the compressor, most larger refrigerationsystems utilize a pressure actuated switch. The bellows or actuator ofthis switch is connected directly to the refrigerant line by a smallcapillary tube so that changes in pressure (and temperature which isdirectly proportional to pressure) result in actuation of the switch andconsequently the compressor.

It has been my experience that one of the very severe shortcomings orweaknesses of a refrigeration system of the type described hereinaboveis the frequency of failure of the system because of a failure of thecapillary tube. Generally, this tube is made from lAG inch copper tubingconnected at one end to the compressor and at the other end to thepressure switch control unit. Frequently, this tube breaks, either as aconsequence of mechanical fatigue or as a consequence of a serviceman orother personnel accidentally bumping it. Breakage of this tube involvesnot only replacement of the tube but much more seriously, replacement ofthe complete charge of refrigerant plus in some instances, loss ofrefrigerated food products. In many larger installations, replacement ofthe refrigerant alone involves an expenditure of hundreds or eventhousands of dollars.

It has, therefore, been an objective of this invention to provide animproved refrigeration system which is not subject to the shortcomingsof conventional systems as outlined hereinabove. Specifically, it hasbeen an objective of this invention to provide a refrigeration systemwhich avoids the severe consequences of failure of the capillary tube ofthe contr-ol system.

Generally, in my improved refrigeration system, the control unit andspecifically the pressure switch of the' con- 3,498,075 Patented Mar. 3,1970 ICC loss of the refrigerant. This isolation is provided by pressureactuated diaphragm motors or bellows located at opposite ends of anon-compressible capillary tube and interconnected by a pressuretransmitting fluid enclosed within the tube.

The primary advantage of the system is that it avoids escapement of therefrigerant into the atmosphere upon failure of the capillary tube.Since, in my experience, or more of all system failures which result inthe loss of the refrigerant occur at this point in the system, thisinvention avoids the severe consequences of most system failures.

These and other objectives and advantages of this invention will be morereadily apparent from the following detailed description of the drawingsin which:

VFIGURE 1 is a diagrammatic illustration of a typical refrigerant or airconditioning system incorporating the novel control unit of thisinvention, and

FIGURE 2 is a side elevational view, partially br-oken away, of thepressure transmitting section of the control unit including the twopressure actuated diaphragm motors or bellows and the interconnectingfluid filled capillary tube.

Generally, the invention `of this application is illustrated as appliedto a c-onventional vapor compression cycle refrigeration or airconditioning system. It should be appreciated, however, that theinventive control unit of this system is equally applicable to othertypes of refrigeration systems. Therefore, the term refrigeration isused generically throughout this application to designate any type ofcooling, refrigerating, or air conditioning system.

The vapor compression cycle refrigeration system illustrated in FIGURE 1is a typical commercially available refrigeration system except for thenovel control portion of the system. Basically, it comprises anevaporator 10, a compressor 12, a condenser 11, a receiver 15, and anexpansion valve 17. Liquid refrigerant boils at a low temperature in theevaporator 10 to produce cooling. From the evaporator, the gaseousrefrigerant is supplied through a conduit 21 via an inlet valve 13 tothe compressor 12 which raises the temperature and pressure of therefrigerant. The gaseous pressurized refrigerant is then fed through aconduit 22 and an outlet valve 14 to the condenser 11 in which heat iswithdrawn from the refrigerant. From the condenser, the refrigerantpasses as a liquid through a conduit 23 and valve 16 to the receiver 15where it is stored. From the receiver, the liquid refrigerant passesthrough an outlet or king valve 18 and conduit 19 through the expansionvalve 17 back to the evaporator. In pass ing through the expansion valve17, the liquid refrigerant expands and changes from the high pressurelevel in the condenser to the low pressure level in the evaporator 10.This flow cycle continues so long as a motor 20 continues to drive thecompressor 12.

The control unit 24 which supplies power to the motor and thus controlsits operation includes a pair of lead wires 25, 26 which interconnectthe motor to an electrical power source 27 through a pair of seriesconnected switches 28, 29. One of these switches 28 is springbiased to anormally open condition and the other 29 is spring biased to a normallyclosed position. Both switches 28, 29 are pressure actuated by diaphragmpiston actuators or motors 30, 31. One switch 28 serves as a controlswitch to cycle the compressor while the other 29 serves as a highpressure safety switch to shut olf the compressor in the event thatpressure in the system exceeds a predetermined safe value, as isexplained more fully hereinafter.

The control unit 24 has only been illustrated diagrammatically since,except for the interconnection or interface between the electricalportion of the unit and the refrigerant flow path, it is a conventionaloff the shelf item of hardware which may be purchased from any ofseveral sources. One such suitable control unit is manufactured by theMilford Division of the Robertshaw Controls Company and is designated astheir Model No. PT 22-7401.

The pressure actuator of switch 28 is connected to another diaphragmmotor 32 via a capillary tube 33, and similarly the diaphragm motor 31is interconnected to a diaphragm motor 34 via a capillary tube 35. Bothdiaphragm motors or actuators 32,` 34 are connected directly to thecompressor 12 by a pair of conventional fittings 36, 37 (FIGURE 2); theactuator 32 being connected to the low pressure side of the compressorand the actuator 34 being connected to the high pressure side. Thus, thediaphragm motor 32 is operable to Sense or respond to changes ofpressure on the low pressure side of the compressor and the refrigerantsystem and the diaphragm motor 34 senses or responds to changes ofpressure on the high pressure side of the compressor and the refrigerantnetwork.

The pressure actuators 30, 32 and transmitting capillary tube 33 areidentical to the actuators 31, 34 and transmitting capillary tube 35 sothat only one pair of actuators and interconnecting tube 33 have beenillustrated in detail. It should be appreciated, however, that anidentical pair of actuators and transmitters are located on the highpressure side of the compressor.

The diaphragm motor or pressure actuator 30 comprises a pair of discs40, 41 brazed together at their peripheral edge so as to define a sealedcentral cavity 43 therebetween. A circular diaphragm spring 45 issandwiched between and sealingly separates the two chambers 46, 47 onopposite sides of the spring 45. This spring 45 is operative to bias apiston 48 of the motor against the inner surface 49 of the plate 41.Sleeves 50, 51 are brazed or welded to opposite sides of the discs 40,41 and are provided with axial apertures 52, 53 co-axial with centralapertures 54, 55 in the discs 40, 41 respectively. The aperture 52 inthe sleeve 50 sealingly receives and is welded or brazed to one end 33Aof the copper capillary tube 33. The opposite end 33B of the tube ismounted within and welded to an identical sleeve of the pressureactuator 32. Sleeve 51 slidingly supports a piston rod 56, one end 57 ofwhich bears against the disc 48 and the opposite end of which contactsthe blade 28A of switch 28. A heavy spring 59 biases the switch 28 to anormally opened position against the bias of the diaphragm spring 45.Generally, an adjustment screw (not shown) is provided to adjust thecompression of the spring 59 and thus the pressure required to close theswitch 28.

The pressure actuator 32 is identical to the actuator 30 except that itdoes not include the piston rod 56. Accordingly, the components of theactuator 32 which are identical to corresponding components of theactuator 30 have been given identical numerical designations followed bya prime mark.

The inexpansible copper capillary tube 33 together with the chamber 46of actuator 30 and chamber 46 of actuator 32 sealingly enclose apressure transmitting fluid, such as a conventional refrigeration oil.One such suitable oil is identified as Suniso 3G refrigerant oilmanufactured by the Sun Oil Company. This is an incompressible oil whichis compatible with the refrigerant of a refrigeration system and has aviscosity rating of SAE 150. Other regrigerant oils having viscosityratings as low as SAE 75 would also be suitable and in some applicationsmight even be preferable. Thus, changes in pressure at the fittings 36of the compressor are operative to move the diaphragm 45 and piston 48of the actuator 32 so as to effect fluid flow of the refrigerant oil inthe capillary tube 33.

Assuming that there is a refrigerant pressure increase in the evaporatorand on the low pressure side of the refrigerant system (and consequentlya temperature increase) the pressure in the chamber -47 of the pressureactuator 32 is increased upon a pressure increase in the chamber 47 ofactuator 32, the piston 48 and diaphragm 45 are moved to the rightforcing fluid from the chamber 46' into the capillary tube 33. Thisfluid ow through the tube 33 results in rightward movement of the piston48 and piston rod 56 of the actuator 30 so as to effect closing of theswitch 28. When the switch 28 is closed, it results in completion of anelectrical circuit to the compressor motor 20 from the power source 27through the series connected switches 28, 29.

Switch 28 is the control switch which cycles the compressor by turningit on when the temperature (and pressure) of the refrigerant in theevaporator and the compressor exceeds a preset value and turning it offwhen the temperature reaches the desired value. The other switch 29 is ahigh pressure safety switch operative to open the motor circuit in theevent that the pressure at the head of the compressor or on the highpressure side of the refrigerant system exceeds a preset safe Value.This might occur in the event of failure of the condenser or of anycomponent in the system. In this event, the actuator 34 senses theunsafe high pressure condition and transmits the high pressure increasethrough the fluid in the capillary tube 35 to the pressure actuator 31to open the switch 29. Thus, the compressor is stopped until thepressure is relieved and the condition corrected.

Because the refrigerant system and the conduits 19, 21, 22, 23 throughwhich the refrigerant is transmitted are physically isolated from thecapillary tubes 33, 35 by the sealed pressure actuators 32, 34, failureof the small capillary tubes does not result in the loss of therefrigerant to the atmosphere. The copper tubes 33, 35 are only 3/16inch in inside diameter while the refrigerant conduits are at least l1/2inch in inside diameter and may go to several inches in diameter. Thus,when tube or conduit failure occurs, it generally is the capillary tubewhich fails and which, prior to this invention, resulted in the loss ofall the refrigerant in the system.

I prefer that the entrapped pressure transmitting fluid in the capillarytubes 33, 35 be a yconventional refrigerant oil such as Sunisco G3. Therequirements of the fluid are that it be stable and non-responsive totemperature or other external environmental conditions and compatiblewith the refrigerant and the refrigeration system so that the oil willhave no detrimental effect upon the system or the equipment if it leaksinto the refrigerant conduits 19, 21, 22 and 23. It must also beoperable to transmit pressure changes through the tube at pressureswhich range from plus 450 pounds per square inch to 27 inches of mercuryvacuum at temperatures which range from plus Fahrenheit to minus 100Fahrenheit. These are the operating pressure and temperature ranges ofconventional refrigeration systems.

While I have only described a single preferred modification of myinvention, those persons skilled in the refrigeration arts will readilyappreciate numerous changes and modifications which may be made withoutdeparting from the spirit of my invention. Therefore, I do not intend tobe limited except by the scope of the appended claims.

Having described my invention, I claim:

1. In combination with a refrigeration cooling system of the type whichcomprises a motor driven compressor for increasing the pressure of arefrigerant material in said system, a condenser for removing heat tocool said pressurized refrigerant material after it exits from saidcompressor, an expansion valve, and an evaporator through which saidcooled pressurized refrigerant passes to extract heat from the areasurrounding said evaporator before being returned to the inlet side ofsaid compressor,

a control unit for controlling the operation of said cornpressor, saidcontrol unit comprising:

a pressure responsive switch operable to control operation of saidcompressor, and

an inexpansible lluid capillary tube interconnecting the liow path ofsaid refrigerant and said pressure responsive switch, the improvementwhich comprises a pair of pressure responsive actuators located atopposite ends of said capillary tube and a pressure transmittingrefrigerant oil fluid medium compatible with the refrigerant in thesystem and sealingly entrapped within said capillary tube between saidpressure actuators, said entrapped refrigerant oil being operable totransmit a pressure change in the refrigerant of said cooling system tosaid pressure responsive switch while maintaining said refrigerantphysically separated from said capillary tube so that a break in saidtube does not result in the loss of said refrigerant to atmosphere, saidrefrigerant oil being operable to transmit pressure changes attemperatures which range from plus 160 Fahrenheit to minus 100Fahrenheit.

2. The control unit of claim 1 wherein said refrigerant oil is operableto transmit pressure changes which range seven inches of vacuum. fromplus 450 pounds per square inch to minus twenty- 3. The combination ofclaim 1 wherein said capillary tube interconnects said pressure switchto the low pressure side of the refrigerant flow path between theevaporator and the high pressure side of the compressor,

4. The combination of claim 1 wherein said capillary tube interconnectsthe pressure switch to the high pressure side of the refrigerant iiowpath between the low pressure side of the compressor and the condenser.

5. The combination of claim 1 wherein said pressure responsive fluidactuators comprise a pair f diaphragm type piston motors.

6. For use in combination with a refrigeration cooling system of thetype which comprises a motor driven compressor for increasing thepressure of a refrigerant material in said system, a condenser forremoving heat to cool said pressurized refrigerant material after itexits from said compressor, an expansion valve, and an evaporatorthrough which said cooled pressurized refrigerant passes to extract heatfrom the area surrounding said evaporator before Ibeing returned to theinlet side of said compressor, a control unit for controlling theOperation of said compressor, said control unit comprising:

a pressure responsive switch operable to control operation of saidcompressor, and

an inexpansible fluid capillary tube interconnecting the flow path ofsaid refrigerant and said pressure responsive switch, the improvementwhich comprises a pair of pressure responsive actuators located atopposite ends of said capillary tube and a pressure transmittingrefrigerant oil compatible with the refrigerant in the system andsealingly entrapped lwithin said tube between said pressure actuators,said entrapped refrigerant oil being operable to transmit a pressurechange in the refrigerant of said cooling system to said pressureresponsive switch -while maintaining said refrigerant physicallyseparated from said capillary tube and said pressure switch so that abreak in said tube does not result in the loss of said refrigerant toatmosphere, said refrigerant oil being operable to transmit pressurechanges at temperatures which range from plus 160 Fahrenheit to minusFahrenheit.

7. The control unit of claim 6 wherein said refrigerant oil is operableto transmit pressure changes which range from plus 450 pounds per squareinch to minus twenty-seven inches of vacuum.

8. The control system of claim 6 wherein said pair of pressureresponsive actuators comprises a pair of diaphragm type piston motors.

References Cited UNITED STATES PATENTS 1,915,498 6/1933 Kellett 20G-83.22,195,220 3/1940 McGrath 62-228 2,512,066 6/1950 Linfor 62-227 XR MEYERPERLIN, Primary Examiner U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Paten: No.3,498,075 Dated March 3 197D Inventor(s) William A. Zumbel It iscertified that error appears in the aboveidentified patent and that saidLetters Patent are hereby corrected as shown below:

Column 2, line 4, delete the word "not" and substitute the word -n'Column 3, line 69, delete the word "regrigerant" and substitute the wordrefrgerant.

Column 5, lines 25 and 26 should be reversed.

SIGNED ND SEALED JUL141970 sEAL) Attest:

Eawml M. member, Jr.

Mening Ofl mmm E. scam, JR.

Gomisslonefr of Patents

